Midterm 3 Practice Test

1. Two blocks collide with a load bang, is mechanical energy conserved during the collision?

(a) No (b) Yes.

2. Three balls of mass 2 kg are placed at the origin, 2 m up the x-axis, and 2 m up the y-axis. What is x_CM?

(a) 1 m (b) 2 m (c) 1/3 m (d) 2/3 m (e) 0 m

3. A 800 kg car is at the top of a 100m hill at which it has a speed v_a, it coasts down a valley and to the top of another 150m hill. Find v_a such that it reaches the higher hill with zero speed.

(a) 980 m/s (b) 31.3 m/s (c) 22.1 m/s (d) 48.3 m/s (e) 15.8 m/s

4. A 1500 kg car is traveling East at 30 m/s while another 2500 kg car, traveling in the same lane, heads West at 20 m/s . What is v_CM?

(a) -1.25 m/s (b) -5000 m/s (c) 23.75 m/s (d) 95,000 m/s (e) -18 m/s

5. Two blocks of mass M and 2M are attached to the ends of a spring. The system is placed on a horizontal frictionless surface, compressed, and released. If v is the speed of the 2M block, what is the total kinetic energy of the system after the masses have flung apart? Neglect the spring mass.

(a) 2M v² (b) 5M v² (c) 4M v² (d) 3M v² (e)M v²

6. [written answer] A clay block of mass 100 kg and speed 3 m/s collides with a clay block of mass m at rest and sticks. During the collision 20% of the initial kinetic energy is dissipated in heat. Find m.

7. [written answer] A particle of mass m is travelling up the y-axis at speed v. It strikes a particle of mass M=400 gm (which was at rest), sending it flying to the right at an angle of 15 degrees with respect to the +y-axis. The original particle flies to the left at 25 degrees with respect to the +y-axis. Determine m.